Wireless networks rely on a large number of individual cells to provide high capacity wireless services over large coverage areas such as market areas (e.g. cities), surrounding residential areas (e.g. suburbs, counties), highway corridors and rural areas. Continuous radio connectivity across these large coverage areas is accomplished via user mobility from one base station to others as the user traverses the network's operating area. High reliability mobility is an important aspect of mobile wireless networks in order to minimize the number of dropped calls or other abnormal discontinuation of radio service to the supported users.
A key feature of modern multi-base station mobility networks is the creation and maintenance of neighbor lists for each base station within the network. Each base station transmits its list of nearby neighbor cells to mobile devices such that a mobile device can continuously monitor the radio frequencies defined in the list and search for higher quality base stations to which it may handover if and when the mobile device experiences degraded signal quality from its current serving radio base station. In other words, during active call sessions, the mobile device continually monitors quality of its serving base station and scans the frequency and/or scrambling code combinations defined on its current neighbor list searching for suitable quality handover candidates.
If the mobile device finds a higher quality signal coming from a defined neighboring base station during this scanning procedure, it initiates a handover request to the network. If the request is granted, the mobile device connects to the candidate base station in either a hard or soft handover mode depending on the particular radio network technology in question. If the original serving base station's signal quality drops below a defined signal quality threshold the mobile device will be connected entirely to the new base station and the call will continue. Should the serving base station's signal quality degrade below an acceptable level prior to the mobile device scanning and locating a suitable high quality neighboring cell, the call will typically fail and the user will experience a disconnect from the system such as a dropped call.
Each base station maintains its own list of likely neighbor cells and communicates this list via over the air messaging to each mobile station within its coverage area. Mobile stations search this list repeatedly and frequently to support handover operations as described above. Automatic Neighbor Relationship (ANR) management functions can assist with the creation and maintenance of these neighbor lists.
One source of data input to ANR routines comes from Detected Set Reporting (DSR) which includes a summary of mobile equipment base station measurement reports. DSR provides information regarding base station pilot signal strength and signal quality as observed by mobile stations operating within the wireless network. These reports associate signal strength and signal quality measurements with base station CDMA scrambling codes but in general do not associate these metrics with a unique cell identifier. In many cellular systems, the unique cell identifier is a Base Station Identifier code (BSID).
BSIDs are unique throughout the network, but BSIDs are not always associated with scrambling codes in ANR equipment. When data is reported from a UE under a scrambling code that is not associated with a cell on a neighbor list of the UE, the identity of an originating cell may not be known to the ANR equipment. Furthermore, scrambling codes are reused multiple times over large wireless market areas, so it is possible for ANR equipment to receive data from multiple base stations with the same scrambling code, resulting in an ambiguous scrambling code. Therefore, it is desirable to map the detected scrambling code to the correct cell identifier of the cell being measured.